ping On Fri, May 07, 2021 at 02:36:48PM +0100, Daniel P. Berrangé wrote: > This is in response to this bug report: > > https://gitlab.com/qemu-project/qemu/-/issues/191 > > The generic 'qemu64' and 'max' CPUs currently defined to report a > family/model/stepping that approximately corresponds to an AMD K7 > vintage architecture. The K7 series predates the introduction of > 64-bit support by AMD in the K8 series. This has been reported to > lead to LLVM complaints about generating 64-bit code for a 32-bit > CPU target > > LLVM ERROR: 64-bit code requested on a subtarget that doesn't support it! > > The bug report is fairly limited, but it suggests LLVM looks at the > family/model/stepping and decides it to be 32-bit, despite qemu64 > reporting it is 64-bit capable. I've not reproduced this myself, > however, so I'm largely trusting the original reporter's diagnosis > > Of course interpreting the family/model/stepping only makes sense > with scoped to the reported vendor ID. Under TCG, the vendor is > honoured, but AFAICT, under KVM the vendor defined by the QEMU > model model is ignored and the real host vendor passed through. > This will make the chosen family/model/stepping non-sensical when > run under KVM on an Intel host. > > None the less these patches change to report a CPUID with the > family, model and stepping taken from a > > AMD Athlon(tm) 64 X2 Dual Core Processor 4000+ > > which is one of the first 64-bit AMD CPUs. This is at least more > accurate in terms of the static CPU model definition, even if it > is still nonsense in the case where KVM overrides the vendor to > be non-AMD. > > Daniel P. Berrangé (2): > i386: use better matching family/model/stepping for 'qemu64' CPU > i386: use better matching family/model/stepping for 'max' CPU > > hw/i386/pc.c | 6 +++++- > target/i386/cpu.c | 12 +++++++++--- > 2 files changed, 14 insertions(+), 4 deletions(-) > > -- > 2.31.1 > >
Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
